Large-scale circulations in an oscillating thermal convection

Abstract eng:
The interaction between large-scale circulations and unstable thermal plumes of air in a horizontally partitioned rectangular enclosure is investigated numerically. Both a hot and a cold plume flows originated at the central vent in the partition are formed when the wall temperature difference (AT) of the upper and the lower parts of the enclosure keeps a constant. When AT is larger than a threshold value, the hot plume is unstable to a small-scale sinuous wave mode with high frequency, while the two symmetric convection circulations in the lower cavity are taken place by a large-scale circulation, whose strength varies with a low frequency. With the increase of AT, different spatiotemporal evolution scenarios are revealed, and it is concluded that the large-scale low-frequency circulations play important roles at high temperature differences.

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